Defiantly will get some extra KW upgrading the intercooler do it before the tune to save you some money. Because your ECU will be squirting extra unused fuel straight through your engine.

Gauges are really just a luxury as you said, i think its a bit of a waste of money when your just running stock boost . There good to tell when you peak boost but most likely just normal driving you can tell for yourself. I reckon get a Boost Controller before a boost gauge anyways but its your money and your car.

I would also suggest a APS cai as it goes in the inner gaurd and less heat is in there. The APS cai is actually made of like ceramic stuff so it always is good for keeping things cool.

Just my 2cents